#include <bits/stdc++.h>
using namespace std;
#define int long long

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;

struct DisjointSet{
	vector<int>parent,sz;
	int size;
	void init(int n){
		size = n;
		parent.resize(n+1); sz.resize(n+1);
		for(int i = 1; i<=n; i++){
			parent[i] = i;
			sz[i] = 1;
		}
	}
	int find(int x){
		if(parent[x]==x)return x;
		return find(parent[x]);
	}
	void Union(int x, int y){
		x = find(x); y = find(y);
		if(x==y)return;
		if(sz[x]<sz[y]){
			parent[x] = y;
			sz[y]+=sz[x];
		}
		else{
			parent[y] = x;
			sz[x]+=sz[y];
		}
	}
};
struct edge{
	int d,x,y;
};

signed main() {
	cin.tie(0)->sync_with_stdio(0);
	int n;
	cin >> n;
	int cur = n+1;
	map<int,vector<int>>hm;
	for(int i = 1; i<=n; i++){
		int k;
		cin >> k;
		for(int j = 0; j<k; j++){
			int d;
			cin >> d;
			hm[d].push_back(i);
		}
	}
	vector<edge>edges;
	DisjointSet ds;
	ds.init(n+1);
	vector<edge>ans;
	for(auto [w, vec] : hm){
		for(int i = 1; i<vec.size(); i++){
			edges.push_back({w,vec[i-1],vec[i]});
		}
	}
	for(auto e : edges){
		int w = e.d; int x = e.x; int y = e.y;
		if(ds.find(x) == ds.find(y))continue;
		ds.Union(x,y);
		ans.push_back(e);
	}
	if(ans.size() < n-1){
		cout << "impossible\n";
		return 0;
	}
	for(auto [w,x,y] : ans){
		cout << x << ' ' << y << ' ' << w << '\n';
	}

	return 0;
}